1. Field of the Invention
The invention relates to a novel tetrahydroxybenzene tetraester derivative having an oxirane ring or an oxetane ring, a composition containing the derivative, a polymer obtained from the derivative or the composition and uses of the polymer.
2. Background of the Invention
When a polymerizable liquid crystalline compound is polymerized in an aligned state, alignment of the molecules in the liquid crystal is fixed, and therefore a polymer having an optical anisotropy is obtained. Accordingly, in recent years, such polymerizable liquid crystalline compounds have been used for molded articles having an optical anisotropy such as polarizing plates and retardation plates (refer to, for example Japanese Patent Application Laid-Open No. 55573/2001).
Liquid crystal compounds having an acryl group are usually used as the polymerizable liquid crystalline compound described above since they have a high polymerization reactivity and the resulting polymers have a high transparency (refer to, for example Japanese Patent Application Laid-Open No. 154019/2001).
However, such liquid crystal compounds having an acryl group are polymerized by photoradical polymerization, and therefore they have to be polymerized under nitrogen atmosphere. When an optical compensation film in a retardation plate of a liquid crystal display is formed on a triacetyl cellulose (TAC) film, which is usually used as a supporting substrate, it is difficult to coat the acryl base liquid crystalline compound described above directly thereon because of an inferior wettability thereof. Further, when a film formed on the other supporting substrate is laminated on a TAC film, an adhesive has to be used since it has a low adhesive property and is liable to be peeled. Accordingly, involved therein are the problems that the production process can not be shortened and that a retardation plate obtained can not be reduced in thickness.
Accordingly, a liquid crystal compound is desired which is readily polymerized by irradiation with a UV ray in the air at room temperature under the presence of a suitable initiator and which is excellent in characteristics such as its coating property and the like.
An object of the invention is to provide a liquid crystal compound which is readily polymerized in the air at room temperature, has a broad temperature range of a liquid crystal phase, which is excellent in characteristics such as a chemical stability, a transparency, a solubility, a compatibility with other polymerizable compounds, a wettability to a supporting substrate, a polymer which is obtained from the liquid crystal compound, has an optical anisotropy, which is excellent in an adhesive property to a supporting substrate, a hardness, a transparency, a heat resistance and a weatherability, has a small photoelasticity (when a film is prepared from it, a change in a refractive index is small when bent) and uses thereof.